Membrane Distillation (MD) desalination has been sought for its unique advantages in fouling resistance and scalability to small system sizes. In previous studies of membrane distillation, the superhydrophobicity of the membrane has been shown to dramatically decrease fouling in adverse conditions, but the mechanism for this decrease has not been well understood. Fouling may also present a problem in other contexts, such as in heat exchangers.
Hydrophobic membranes are used for a wide range of applications, including membrane distillation, pervaporation, oil-water separation, venting gas from fluid channels, filtration, biological applications and water-proof textiles. Biological applications include medical diagnostics and blood type determination.
Hydrophobic membranes for these applications are typically fabricated from PTFE, PVDF, polyethylene or polypropylene. Fabrication methods include phase-inversion, electrospinning, sintering and stretching. Hydrophilic/hydrophobic hybrid membranes made from hydrophilic materials treated with fluoropolymers or other non-polar materials may also be used.
Many hydrophobic membrane processes depend on maintaining the resistance of the membrane to wetting. If wetting occurs, contamination, degradation of process quality and accuracy, and reduction in transmembrane flux often follow. A method and apparatus for restoring membrane hydrophobicity, particularly in the context of membrane distillation desalination, is described herein.